In the existing safety device of folding knife, specifically liner lock folding knife, the switch of the safety device is generally provided with independent spring component, and due to such a structure, it is not convenient to be installed and it is easy to cause low stability because of the spring. Additionally, in most cases, the switch of the safety device is provided at a middle position of outer side surface of the handle, and due to such a structure, it is not convenient to operate and it affects the appearance of the handle.